Vacuum ash handling system



Sept. 10, 1957 T. E. PYNOR VACUUM ASH HANDLING SYSTEM 2 Sheets-Sheet lfiled July 8, 1954 Z L. L T lNl/i/VTOR HOMES ERC PYNOR ATTORNEY Sept.10, 1957 T. E. PYNOR 2,80

VACUUM ASH HANDLING SYSTEM Filed July 8, 1954 2 Sheets-Sheet 2 INVENTOR.THOM As ERIC PYNOR A TTOR/VEY' United States messes VACUUM ASH HANDLINGSYSTEM Thomas Eric Pynor, Port Kennedy, Pa., assiguor to Beaumont BirchCompany, Philadelphia, Pa., a corporation of Pennsylvania ApplicationJuly 8, 1954, Serial No. 442,107

19 Claims. (Cl. 3(i227) The present invention relates to ash handlingsystems, and particularly to ash handling systems for power plants andother large boiler installations, where the problem of ash removal anddisposal in large quantities, continuously from a plurality of ashproducing units, is an important one.

In power plants of the coal burning type, and likewise in heating plantswhich utilize coal or other combustible material as fuel, the productionof ash from the various units is substantially continuous and varies inquantity depending upon the load imposed upon the power or heatingplant, as the case may be.

In such plants, it is customary to have a plurality of boiler or otherash producing uits, which may be operated or shut down in varyingnumbers, as required, to meet the varying load conditions. By utilizinga number of smaller units, rather than one large unit, greaterflexibility may be obtained in carrying the load most economically.However, with an increasing number of boiler or other combustion and ashproducing units, the problem of ash removal becomes greater inproportion. The greater the number of'units, the greater the problem,both as to quantity of ash removed and attendance required to effectremoval of the ash in such a manner as not to interfere with propercombustion.

With modern power plants, and to a certain extent with heating plants,automatic operation is desirable for the reason that varying loadconditions may be met best by means responsive to variations in loadconditions, and also for economy in operation and certainty of controlbeyond anything possible with direct control by operators. Likewise, itis desirable to provide ash handling equipment for removing the ashaccumulation substantially continuously and in accordance with theproduction of the ash, which in turn, as hereinbefore indicated, dependsupon the varying load conditions imposed upon the plant. In addition, itis desirable in large boiler installations, to provide for the controlof all units from a centralized location, such as a panel convenientlylocated within the plant, not only to indicate the condition ofoperation of the system, but also to provide a record of anyirregularity in the operation.

In coping with the ash handling problems presented by modern powerplants and other large boiler installations, the type of ash handlingsystem which includes a conduit system for ash removal by vacuum hasbeen employed to advantage. Reference may be had to the pendingapplication of William D. Hughes, Serial No. 169,492, filed June 21,1950, now Patent No. 2,706,136 April 12, 1955, for a detaileddescription of one such ash handling system, which involves not only theproblem of maintaining the vacuum in the conduit system while feedingmaterial therethrough, but additionally the problem of sequentialcontrol of a conduit system involving a plurality of feeding units foreach boiler. Briefly, the vacuum is created in the conduit system by asteam jet under electrical control, and the electrical system iscontrolled by a vacuum switch also connected with the vacuum sys-Fatented Sept. 10, 1957 rCQ directly into the conduit system from eachboiler or other ash producing unit. Between the vacuum switch and thefeeder units is an electrical control system embodying a number ofelectrical control and timing relays, together with electrical circuitsproviding for both individual and joint control of all boiler units bothautomatically and manually, as well as indicating and recording elementsas required for continuous operation of the plant.

The type of ash handling system just described is subject to thedisadvantage that frequently false indications of operating conditionsoccur, adversely affecting the efiiciency of the ash handling system byprematurely terminating operation of one feeder unit and commencingoperation of the next. An important factor which tends to cause falseindications is that fly ash may be fed into the conduit system by onefeeder unit, bottom ash by the next and soot by another, or fly ash,bottom ash or soot may be fed each at a dilferent time by the samefeeder unit into the conduit system. These materials have physicalcharacteristics which distinguish them each from the others and afiectthe systems ability to sustain a vacuum. For example, the lighter thematerial discharged by a feeder unit into the conduit system, the morerapidly the vacuum in the conduit system decays, as a consequence ofwhich the vacuum in the conduit system may drop to a minimum not becausea feeder unit is empty but because the system is unable to preventexcessively rapid decay of the vacuum in the conduit system when thematerial discharged by the feeder unit into the conduit system is toolight in weight.

Another factor which tends to cause false indications is that for eachdifferent material to be handled the ideal adjustment of the vacuumswitch is different. However, there is only one vacuum switch and onlyone selected adjustment thereof is possible. This selected adjustment ofnecessity is a compromise adjustment made not to meet the demands of aselected material to be handled, but to meet as nearly as possible thedemands of all the materials to be handled.

Still another factor which tends to cause false indication is that avacuum switch is responsive only to substantial changes in vacuum, andtherefore changes in the vacuum in the conduit system must be in theorder of onehalf inch or more of mercury before the vacuum switch willrespond.

The ash handling system described hereinabove is subject to the furtherdisadvantage that any indication of material flow in the conduit systemis dependent upon indication of vacuum in the conduit system. Thisdependence is undesirable because the physical characteristics of thematerial being handled may be such that the vacuum in the conduit systemremains substantially unchanged whether or not there is a flow ofmaterial, as a consequence of which there may be a flow of materialwithout any indication thereof. Still another disadvantage is thatinitial installation of a vacuum switch is comparatively complicatedbecause such a switch must be piped to the conduit system. Furthermore,a vacuum switch requires very careful adjustment in order to respond tothe best of its ability to changes in vacuum in the conduit system.

It is, therefore, a primary object of this invention to provide improvedmeans for controlling the operation of an ash handling system of thetype including a conduit for ash removal by vacuum wholly automaticallyfrom various points in the conduit in predetermined sequence, ormanually, selectively from various points in the conduit in anysequence.

Another object of this invention is to provide such an ash handlingsystem with improved control means which is responsive to the degree towhich the conveying me 6 dium is laden with ash, irrespective of vacuum,as a consequence of which there is eliminated any compromise adjustmentof the control means due to varying physical characteristics of theseveral materials to 'be handled.

And another object of this invention is to provide such an ash handlingsystem with improved control means including photoelectric cell andlight source means, which is substantially more responsive to changes inthe degree to which the conveying medium is laden with ash than a vacuumswitch is to changes in vacuum in the conduit.

Still another object of this invention is to provide such an ashhandling system with more reliable means for indicating the flow ofmaterial in the conduit, such means being more reliable by reason ofbeing independent of vacuum in the conduit.

And sti-ll other objects of this invention are to provide such an ashhandling system with control means which is comparatively simple toinstall and easy to adjust, which affords increased protection againstdrawing hot gases through the system.

The invention .will be further understood from the following descriptionwhen considered in connection with the accompanying drawings, in which apresent preferred ash handling system and control means therefor areshown for a multiple unit boiler plant of the type used for steam drivenpower plants and the like, and its scope is defined by the appendedclaims.

In the drawings:

Figure 1 is a schematic diagram showing an ash handling conduit systemand feeder and control means arranged in accordance with the presentinvention;

Figure 2 is an enlarged vertical section taken on line 2-2 of Figure 1;

Figures 3 and 4 are fragmentary vertical sections taken on line 3-3 ofFigure 1 respectively showing different arrangements of the parts; and

.Figures 5 and 6 are vertical sections taken respectively ou lines 5-5of Figure 3 and line 6-6 of Figure 4.

Referring to Figure l, a branched closed conduit system is shown for ashremoval from two boilerunits of a power plant. The system includes anumber of main conduit branches of which only branches 1%) and 11 areshown. The latter respectively serve boilers 12 and 13 indicatedgenerally by the center lines shown in the figure. The main conduitbranches in and 11 are each supplied with ash through feeder units, themain conduit branch being provided with rotary feeder valves or gates14, 15, 16 and 17, and the main conduit branch 11 being provided withrotary feeder valves or gates .18, 19, 20 and 21.

It will be noted that the main conduit branches 10 and 11 areadditionally provided respectively with cutoff gates 22 and 23, andstack hoppers 24 and 25 are connected respectively with the main conduitbranches 10 and 11 through cut-off gates 26 and 27, all of which gatesare arranged to be electrically operated through solenoid elements,indicated at 28, connected electrically with the remainder of thesystem.

The rotary feeder gates are each provided with a hopper 29 and are eachdriven by an electric motor 30 through a suitable belt drive asindicated. Any suitable feeder unit may be used, but it may be assumedthat each feeder unit is of the rotary-vane type for carrying the ashfrom the hoppers into the conduit system when operated by the motormeans. Each motor 30 is provided with a control unit, as indicated at31, connected electrically with the remainder of the system.

It will be noted that the ash conveying main conduit branches 10 and 11are joined with a common conduit section 32, in which is located a steamjet 33 directed to produce a vacuum on the system when supplied withsteam, the supply of steam being controlled by a steam valve (not shown)connected electrically with the remainder, of the system. The commonconduit section 32 is connected with a relatively large ash receiver andseparator unit 34, into which it discharges the ashes and other productsof combustion drawn from the main conduit branches 10 and 11. Theash-free air is discharged through the open top outlet conduit 35, whilethe ashes are removed from a suitable ash hopper, as indicated at 36, atthe bottom of the separator unit. The handling of the ashes beyond thispoint does not concern the present invention.

in construction and operation the ash handling system of the presentinvention generally is similar to that disclosed in the pendingapplication of William D. Hughes, to which reference may be had fordetails of construction and operation not set forth herein. Of course,the disclosure of only two main conduit branches in the system of thepresent invention is merely for the purpose of illustration. It will beunderstood that the number of such branches may be reduced to one 'orincreased to three, as disclosed in the aforementioned pendingapplication, or even more. The system of the present invention and thatof the aforementioned pending application do differ essentially in thatthe electrical means which controls the latter system is arranged torespond to the operation of a vacuum switch, whereas that which controlsthe system of the present invention is arranged to respond instead, tothe operation of light source and photoelectric cell means now to bedescribed.

The light source and photoelectric cell means includes a light sourceunit 37 and :a photoelectric cell unit 38 connected into the system forcontrol purposes, extending.

outwardly preferably horizontally respectively from opposite sides ofthe conduit section 32. The light source and photoelectric cell unitsare carried by the conduit section 32, which is common to the mainconduit branches 10 and 11. For connecting the light source andphotoelectric cell units into the common conduit section 32,diametrically opposed portions of the wall of the conduit are providedrespectively with a pair of axially aligned integral bosses 39-39 whichproject outwardly therefrom in opposite directions. The bosses 39-39 areprovided each with an external flange 40 and a central bore having atapered outer portion, as indicated at 41, and a constricted innerportion which communicates with the interior of the conduit section 32,as indicated at 42.

The bosses 39*39 carry respectively a pair of sleeves 43-43 each ofwhich is provided with an external flange 44 and external threadsrespectively at opposite ends thereof. For mounting the sleeves '43-43,the flanges 44-44 are conventionally bolted respectively to the flanges40-40 of the bosses 39-39, as indicated at 45, and when the sleeves43-43 are thus mounted they communicate respectively with the centralbores which extend through the bosses 39-39.

The sleeves 43-43 carry respectively a pair of fittings 46-46 each ofwhich is provided with parallel external flanges 47 and 43 respectivelyat opposite ends and a deep annular groove 49 in one face disposed inconcentric relation to a central bore, there being thus formed a pair ofaxially extending concentric annular walls 50 and 51, th wall 59defining the central bore and the walls 50 and 51 defining the groove49.

The fittings 46-46 carry a pair of centrally apertured plates 52-52. Formounting the plates 52-52, the same are conventionally boltedrespectively to the wall '50 of the fitting 46, as indicated at 53, andto the wall 51 of the fitting 46, as indicated 'at 54, and when theplates 52-52 are thus mounted the grooves 49-49 of the fittings 46-46are closed so as to form annular chambers. The central bores through thefittings 46-46 are each provided with a portion 55 which is proximatethe plate 52 and a reduced bore portion 56 which is proximate the flange48 of the fitting 46, an annular shoulder 57 being formed Where thediameter of the bore changes. A lens 58 is fitted into the bore portion55 and is seated against the shoulder 57, being conventionally securedagainst removal as by a split ring 59. g a

For mounting the assemblies each comprising a fitting 46, a plate 52 anda lens 58, th annular walls 50-50 of the fittings 46-46 are providedwith internal threads through the medium of which the aforementionedassemblies are secured respectively upon the sleeves 4343. The annularWalls 50-50 of the fittings 46-46 are additionally provided each with agroup of four circumferentially equally spaced radially extendingopenings 60 which place the annular chamber 49 in communication with thebore portion 55 of the central bore through the fitting 46, and theannular walls 5151 of the fittings 4646 are provided each with a groupof four circumferentially equally spaced radially extending openings 61which place the annular chamber 49 in communication with atmosphere. Itwill be noted that the openings 60 in the annular Walls 50 are axiallyalined respectively with the openings 61 in the annular walls 51. Thelight source unit 37 and the photoelectric cell unit 38 projectoutwardly respectively from the fittings 4646. The light source unit 37is provided with a casing 62, a lense board 63 and a len 64, while thephotoelectric cell unit 38 is provided with a casing 65 and a shutter66, a lense board 67 and a lens 68.

The light source unit 37 is suitably connected through leads in aconduit 69 with a source of electricity, while the photoelectric cellunit is connected electrically through leads in a conduit 70 with theremainder of the electrical system. The light source and photoelectriccell units per so may be of any conventional construction, and,therefore, a further detailed description thereof is believed to beunnecessary except to point out that the photocell unit is operativewhen influenced by light to produce an electric current, which may beamplified as desired, suficient to energiz an electrically operatedsequential control relay or other device for controlling the operationof the ash conveying system or any desired part thereof. Preferably, theterminal leads 80-8!) of the photocell unit 38 are electricallyconnected to a relay 81 for controlling the operation of a switch 82 thecontacts 83 and 84 of which are normally closed when th amount of ashbeing conveyed through the discharge conduit is reduced to substantiallyzero or a predeterminedly established minimum, whereupon the electricalcontrol circuit is rendered effective to operate the conveying system asrequired.

The light source unit 37 projects a beam of light across the interior ofthe conduit section 32, the light beam passmg through the lenses64585868 to the photoelectrio cell unit 38. The intensity of the light,beam at the photoelectric cell unit38 depends in part upon the intensityof the light beam at its source and in part upon the light passingcapacity of the lenses 58-58. The latter are made preferably of clearglass, but, of course, in the operation of the ash handling system someash will settle upon the inner faces thereof, reducing their lightpassing capacity and correspondingly reducing the intensity of the lightbeam projected as aforementioned. When the ash handling system is undervacuum, excessive reduction in the light passing capacity of the lenses5858 is avoided through the medium of openings 69 and 61 and the annularchambers 4949 of the fittings 46-46. Air from atmosphere is drawnthrough the openings 61into the annular chambers 4949, from the chambers49-49 through the openings 60 into the bore portions 5555 of thefittings 46-46, and from the latter through the sleeves 43-43 and thebosses 39-39 into the interior of the conduit section 32. The inrushingash-free air streaming across the faces of the lenses 5S58 insuresagainst excessive accumulations of ash on their inner faces and in thepassages communicating with the interior of the conduit 32. In the eventthat the ash handling system operates under positive instead of negativepressure, excessive reduction in the light pass g p y of t lenses 58-58is avoided by plugging, in each of the fittings 49-49, all but one ofthe openings 61, as indicated at 71, and supplying ash-free air (oranother gaseous agent) under suitably higher pressure than thatprevailing in the conduit to the annular chambers 49-49 through conduits7272 connected respectively into the unplugged openings 6161.

The intensity of the light beam when it reaches the photoelectric cellunit 38 additionally depends upon the degree to Which the conveyingmedium in the conduit section 32 is laden with ash, it being understoodthat the conveying medium may be air from atmosphere or some othergaseous agent and that the term ash is used herein and in the appendedclaims broadly to designate not only finely divided solid products ofcombustion variously known as dust, fly ash, precipitator ash, soot,bottom ash and the like, but additionally any other air-conveyablematerial which resists the penetration of light. The greater the volumeand accordingly the light-obscuring density of the ash present in theconveying medium, the more the intensity of the light beam is reduceduntil the light beam is totally obscured and fails to penetrate to thephotoelectric cell 38.

Normally the condition of the lenses 5858 is such that approximately 60per cent of the light projected by the unit 37 is obscured, irrespectiveof ash in the conduit section 32. However, the amount of obscurity mayvary between percent and the aforementioned 60 percent, depending uponthe degree to which the conveying medium is laden with ash. Thephotoelectric cell unit 38 is arranged to respond to a highly selectiveamount of obscurity ranging between the aforementioned total and minimumobscurities. As a hopper 29 is emptied, the amount of ash in theconveying medium is decreased with resulting decrease in the degree ofobscurity to passage of light to the photoelectric cell unit 38. Whenthe degree of obscurity has dropped to a predeterminedly establishedvalue, the effective intensity of the light projected to thephotoelectric cell unit 38 is translated by said unit into an electricalcurrent capable of rendering effective the electrical circuit forcontrolling the operation of the ash conveying system. When the flow ofash through the discharge conduit is reduced to a predetermined minimum,as when a given hopper is emptied of its complement of ash to bedischarged into the conduit, the photoelectric cell will be activated toelectrically indicate this prevailing condition upon a suitableindicator included in the electrical control circuit. The electricalcontrol means is so arranged and operative that upon the continuance ofthe aforementioned indication for a predetermined period of time, theash removing operation Will be shifted to another hopper through themedium of an electrically operated sequence contactor suitably includedin the electrical control circuit.

While any suitable electrical control circuit may be employed foreifecting any desired sequential discharge of ash from the severalhoppers 29 by selective operation as desired of the rotary feeder gatesof the several hoppers and of the cut-off gates respectively included inthe several branches of the conduit system, it will be understood thatthe electrical circuit, which is triggered and controlled by thephotoelectric cell unit, hereinbefore described, preferably includes anelectrically operated time delay relay which is immediately associatedwith and operated by the photo-cellunit for effecting the operation inturn of a sequence contactor of the several gates of the conduit systemthrough which ash may be dis charged into the conveying medium. Theelectrical system also includes electrically operated cam timers andcontrol relays for opening and closing the supply valve (not shown) forthe steam which is discharged by the steam jet 33 to induce thenecessary vacuum in the ashconveying conduit system, it being thegeneral practice to time the operation of the steam supply valve so thatit is alternately open for SOseconds and closed for 50 seconds. I V

As has been previously indicated, the time-delay relay which isinterposed in the electrical circuit between the photoelectric cell unitand the sequence contractor is timed to operate the sequence contactorand step it from one contact to a next succeeding one" thereof only uponelapse of 15 seconds following complete evacuation of ash from theconveying system. Should the conveying medium in the region of thephoto-cell unit contain ash in an amount sufiicient to .ei fectivel'yreduce the intensity of the light from the light source to a point wherethe light at the photo-cell unit is not enough to energize thephoto-cell unit, then the time-delay relay remains ineffective toadvance the sequence contactor for establishing the electrical circuitnecessary to effect discharge of ash from the next ash-dischargingstation of the system. Also, should a given station fail to elfectcomplete discharge of its ash within the first 35 seconds of the 50second on period of vacuum in the ash-conveying line, thereby leavingless than 15 seconds of such on period for complete evacuation of ashfrom the line, the time-delay relay operates to hold the sequence.contactor in position to further effect discharge of ash from the givenstation immediately following expiration of the second off period andresumption of the 50 second on period of operation of thevacuum-producing steam jet. This cycle of operation is repeated so thatthe several ash-collecting hoppers respectively completely dischargetheir complements of collected ash into the ash-conveying 'linesequentially in accordance with the operation of the sequence contactor.It will be understood, of course, that for proper sequential operationand discharge of the several ash-collecting units of the system, theelectrical control circuit will include such auxiliary time-delay andcontrol relays and other electrically operated. devices as may benecessary, in connection with which reference is made to the aforesaidPatent 2,706,136, for disclosure of an illustrative electrical circuitwhich is triggered by a vacuum switch instead of by the photo-sensitivemeans of the present invention.

The utilization of the photo-sensitive means of the present invention inthe ash-conveying system of the character above described for triggeringand controlling the operation thereof provides important advantages overuse of the conventional vacuum-switch. As will be apparent,vacuum-switch control of the conveying system is sensitive to variationsin the degree of vacuum present in the ash-conveying line and when it isconsidered that a given hopper in the system may discharge alternatelyfly ash and bottom ash it will be appreciated that substantialfluctuations may occur in the amount of vacuum in the line due entirelyto ditferent densities of the material conveyed therethrough. Of course,the vacuum-switch is initially operatively adjusted to effect sequentialoperation of the several hoppers of the system operating at apredetermined average degree of vacuum best suited for corn veyingmaterial of quite different densities. This adjustment at best is but acompromise, because the switch adjustment ideal for handling fiy-ash,for example, is not ideal for handling bottom ash, and such compromisedadjustment of the vacuum switch for any particular asheonveying systemgives rise to false indications of the amount of material present in theline and frequently results in discharge of ash from a hopperprematurely in advance of one not already completely emptied of ash.

Should the vacuum switch be set for selective operation at a relativelylow degree of vacuum, as for handling exceedingiy light weight material,it may and does frequently happen that upon complete discharge of suchmaterial from a given hopper of the system, the resulting vacuumdifferential is insuflicient to effect operation of the vacuum switch inconsequence of which there is nosequential advance from said givenhopper to another hopper and the system thus remains practicallyinoperative assists even 'though'the vacuum in the line has dropped to aminimum.

,In contradistinction to the above, the photosensitive means of thepresent invention insures sequential operatoin of the several hoppers.of the system regardless of fluctuations in the degree of vacuumprevailing in the system, and is much more sensitive to minutevariations in .the light-obscuring density of the material present inthe conveying medium than is the vacuum switch to cor- .rnit only 40percent of the light from the light source to' respondingly minutefluctuationsin the degree of vacuum necessary for conveying the materialthrough the conduit.

Even though, as above pointed out, the lens obscurity to light of thephotosensitive means may be such as to perproject onto the photocell,the remaining effective light is more than sufiicient to activate thephoto-cell for any desired operating conditions. In actual practice, thephotocell is adjusted for energization of its electrically connectedtimer-relay to effect sequential operation in turn of the sequencecontactor when a predetermined amount of light traverses the conduit andis directed upon the photocell. The light effective for this purpose iswithin the 40 percent range available. Any intensity of this availablelight may be utilized as the minimum below which the photocell remainsunenergized and above which it becomes energized to trigger theelectrical control circuit for the system, and may be selected as thezero value which corresponds to the absence of any ash in the conveyingmedium, any change in such intensity being in accordance with andmeasure of the volume of the lightobscuring ash in the line.Consequently, the presence or absence of ash in the conveying conduit inthe immediate region of the photosensitive means renders the lattereffective to trigger and control the electrical control circuit of thesystem independently of any vacuum fluctuations in the ash-conveyingline.

In addition to the timer and control relays and other devices normallyincluded in the electrical circuit which is controlled by thephotosensitive means of the present invention, there may be includedalso in such circuit means for electrically indicating and recording thecondition of the system during operation thereof. The indicating meansmay be an instrument mounted upon the instrument panel of the system forvisually indicating the volume or light-obscuring density of the ash orother material present in the conveying medium, the instrument beingsuitably calibrated for varying degrees of obscurity from zero up.

The condition of the discharge system at each boiler outlet may berecorded automatically by suitable stylus recorders also mounted on theinstrument panel, the number of these recorders corresponding to thenumber of automatically operated feeder gates. Any conventional types ofindicating and recording means may be employed and inasmuch as theyconstitute no part of the present invention, no description thereof isdeemed to be necessary.

It will be understood, of course, that the present invention issusceptible of various changes and modifications which may be made fromtime to time without departing from the general principles or realspirit of the invention and it is accordingly intended to claim the samebroadly, as well as specifically, as indicated in the appended claims.

What is claimed as new and useful is:

1. An ash handling system for ash producing means comprising conduitmeans, valved means operatively interposed between said ash producingmeans and said conduit for controlling the discharge of ash from saidash producing means into said conduit at a plurality of differentpoints, electrically operated means for periodically applying a vacuumto said conduit for drawing therethrough an ash conveying medium, andphotosensitive means on the downstream side of all of said diiferentpoints of discharge into said conduit means and responsive toapredetermined intensity of light projected across 9 the path of saidconveying medium for initiating the actuation of said valved means insequence.

2. An ash handling system for a plurality of ash producing unitscomprising an ash conveying conduit, electrically operated ash feedermeans connected with said conduit at each of said ash producing unitsfor feeding ash to said conduit from each of said units, electricallyoperated means for periodically applying a vacuum to said conduit fordrawing therethrough an ash conveying medium, and electrical controlmeans including a light source unit for projecting a beam of lightacross the path of the conveying medium at a point on the downstreamside of all of said ash feeder means, and a photoelectric cell unit forreceiving said light beam and responsive to a predetermined intensitythereof for effecting sequential operation of said feeder means.

3. An ash handling system as defined in claim 2, wherein theelectrically operated ash feeder means are further sequentiallycontrolled by electrical timing relay means providing a predeterminedtime of operation for each of the feeder means, and wherein said timingrelay means is controlled by an additional relay means in turncontrolled by the light source and photoelectric cell units, wherebywhen the intensity of the light beam at the photoelectric cell unitincreases to a predetermined point in response to reduction in thedegree to which the conveying medium is laden with ash, the operation ofthe system is advanced.

4. An ash handling system for a plurality of ash producing unitscomprising an ash conveying conduit having a branch for each ashproducing unit, electrically operated ash feeder means connected witheach conduit branch and the associated ash producing unit for feedingash to said ash conveying conduit, electrically operated means forperiodically applying a vacuum to said conduit for drawing therethroughan ash conveying medium, and electrical control means including a lightsource unit for projecting a beam of light across the path of theconveying medium, and a photoelectric cell unit for receiving said lightbeam and responsive to a predetermined intensity thereof for effectingsequential operation of said feeder means, said light source andphotoelectric cell units being associated with a section of said conduitinto which the several conduit branches aforesaid commonly discharge.

5. An ash handling system as defined in claim 4, wherein the ash feedermeans are sequentially responsive through electrically operated timingrelays one for each ash producing unit, and wherein the timing relaysare selectively controlled by said light source and photoelectric cellunits. 6. An ash handling system for a plurality of ash producing unitscomprising an ash conveying conduit having a branch for eachashproducing unit, electrically operated means for periodically applyinga vacuum to said conduit to eifect ash Withdrawal thereto, a pluralityof electrically operated ash feeding devices for each ash producing unitconnected with a branch of said conduit, electrically operated gatemeans for selectively placing each conduit branch in operation, andphotosensitive means responsive to the degree of light-obscurity or" theash present in the ash conveying conduits for controlling the operationof the system, and means providing sequential control of the ash feedingdevices of the system.

7. An ash handling system for ash producing means comprising conduitmeans, valve means operatively interposed between said ash producingmeans and said conduit for controlling the discharge of ash from saidash producing means into said conduit at a plurality of differentpoints, means for applying a vacuum to said conduit, means forprogressively actuating the valve means including a photosensitivedevice on the downstream side of all of said different points ofdischarge into said conduit means and responsive to the light-obscuringdensity of the ash in the conduit.

- 8. An ash handling system for ash producing means comprising conduitmeans, valved means operatively interposed between said ash producingmeans and said conduit for controlling the discharge of ash from saidash producing means into said conduit at a plurality of differentpoints, means for applying a vacuum to said conduit, valve controlmeans, and automatically actuated electrical control means including adevice on the downstream side of all of said different points ofdischarge into said conduit means and which is sensitive to lightpenetrating the ash present in the conveying medium for energizingsuccessively the valved means aforesaid.

9. In an ash handling system, a conduit for a gaseous ash conveyingmedium, means for feeding said conduit with ash to be conveyed throughsaid conduit by said gaseous medium, and electrical control means forsaid ash feeding means including photosensitive means responsive to thedegree to which said gaseous medium is laden with ash, saidphotosensitive means including a member through which light may pass andwhich is disposed in sealing relation to a passage for light formed inthe wall of said conduit, a photoelectric cell, means for projecting abeam of light across the interior of said conduit and through saidsealing member to said photoelectric cell, and means for directing anash-free gaseous medium across the inner face of said sealing member toinsure against the excessive accumulation of ash thereon.

10. In an ash handling system, a conduit for a gaseous ash conveyingmedium, means for feeding said conduit with ash to be conveyed throughsaid conduit by said gaseous medium, and electrical control means forsaid ash feeding means including photosensitive means responsive to thedegree to which said gaseous medium is laden with ash, saidphotosensitive means including a pair of members through which light maypass and which are disposed in sealing relation respectively to a pairof passages for light formed in the wall of said conduit, aphotoelectric cell, and means for projecting a beam of light through oneof said sealing members, across the interior of said conduit and throughthe other of said members to said photoelectric cell, and means fordirecting an ash free gaseous medium across the inner faces of saidsealing members for insuring against the excessive accumulation of ashthereon.

11. In an ash handling system, a conduit for a gaseous ash conveyingmedium, means for feeding said conduit with ash to be conveyed throughsaid conduit by said gaseous medium, and electrical control means forsaid ash feeding means including photosensitive means responsive to thedegree to which said gaseous medium is laden with ash, saidphotosensitive means including means having formed therein a pair ofelongated passages for light extending laterally outwardly respectivelyon oppo site sides of said conduit and communicating with the interiorthereof, a pair of members through which light may pass disposed insealing relation respectively to the outer ends of said passages, aphotoelectric cell, means for projecting a beam of light through one ofsaid sealing members, across the interior of said conduit and throughthe other of said sealing members to said photoelectric cell, and meansfor directing an ash-free gaseous medium across the inner faces of saidsealing members and through said passages for insuring against theexcessive accumulation of ash on said faces or in said passages.

12. In an ash handling system, a conduit under vacuum for drawingtherethrough an ash conveying medium, means for feeding said conduitwith ash, and electrical control means for said ash feeding meansincluding photosensitive means responsive to the degree to which saidconveying medium is laden with ash, said photosensitive means includinga pair of transparent members disposed in sealing relation respectivelyto a pair of passages for light formed in the wall of said conduit, aphotoelectric cell, and means for projecting a beam of light through oneof said transparent sealing members, across the inassists terior of saidconduit and through the other of said sealing members to saidphotoelectric cell, and means associated with said transparent sealingmembers through which, when said conduit is under vacuum, air fromatmosphere is drawn across the inner faces of said transparent sealingmembers for insuring against the excessive accumulation of ash thereon.

13. In an ash handling system, a conduit under positive pressure forforcing therethrough an ash conveying medium, means for feeding saidconduit with ash, and electrical control means for said ash feedingmeans including photosensitive means responsive to the degree to whichsaid conveying medium is laden with ash, said photosensitive meansincluding a pair of transparent members disposed in sealing relationrespectively to a pair of passages for light formed in the wall of saidconduit, a photoelectric cell, and means for projecting a beam of lightthrough one of said transparent sealing members, across the interior ofsaid conduit and through the other of said sealing members to saidphotoelectric cell, and means associated with said transparent sealingmembers through which, when said conduit is under said positivepressure, a gaseous medium under suitably higher pressure is directedacross the inner faces of said transparent sealing members for insuringagainst the excessive accumulation of ash thereon.

14. In an ash handling system, a conduit under vacuum for drawingtherethrough an ash conveying medium, means for feeding said conduitwith ash, and electrical control means for said ash feeding meansincluding photosensitive means responsive to the degree to which saidconveying medium is laden with ash, said photosensitive means includingmeans having formed therein a pair of elongated passages for light, saidpassages extending laterally outwardly respectively on opposite sides ofsaid conduit and communicating with the interior thereof, a pair oftransparent members disposed in sealing relation respectively to theouter ends of said passages, a photoelectric cell unit carried by one ofsaid sealed means, a light source unit carried by the other of saidsealed means for projecting a beam of light through one of saidtransparent sealing members, across the interior of said conduit andthrough the other of said transparent sealing members to saidphotoelectric cell, said sealed means being provided each with aplurality of openings through which, when said conduit is under vacuum,air from atmosphere is drawn across the inner faces of said transparentsealing members for insuring against the excessive accumulation of ashthereon.

15. A material handling system comprising conduit means, valved meansfor controlling the delivery of material into said conduit at aplurality of difierent points, means for producing in said conduitmovement of a material conveying medium, and photosensitive meansresponsive to a predetermined intensity of light projected across thepath of said conveying medium at a point on the downstream side of allof said different points of discharge into said conduit means forinitiating the actuation of said valved means in sequence.

16. An ash handling system for a plurality of ash prot 12 ducing unitscomprising an ash conveying conduit, electrically operated ash feedermeans connected with said conduit at each of said ash producing unitsfor feeding ash to said conduit from each of said units, electricallyoperated means for periodically producing flow through said conduit ofan .ash conveying medium, and electrical control means including a lightsource unit for projecting a beam of light across the path of theconveying medium at a point onthe downstream side of all of said ashfeeder means, and a. photoelectric cell unit for receiving said I lightbeam and responsive to a predetermined intensity thereof for effectingsequential operation of said feeder means.

17. An ash handling system for ash producing means comprising conduitmeans, valve means operatively inter posed between said ash producingmeans and said conduit for controlling the discharge of ash from saidash producing means into said conduit at a plurality of differentpoints, means for creating an air flow through said conduit forconveying ash therethrough, means for progressively actuating the valvemeans including a photosensitive device on the downstream side of all ofsaid different points of discharge into said conduit means andresponsive to the light-obscuring density of the ash in the conduit.

18. A material handling system comprising conduit means, valved meansfor controlling the delivery of said material into said conduit at aplurality of different points, means for efiecting flow of a gaseousmedium through said conduit for conveying said material therethrough,valve control means, and automatically actuated electrical control meansincluding a device on the downstream side of all of said differentpoints of discharge into said conduit means and which is sensitive tolight penetrating the material present in the conveying medium forenergizing successively the valved means aforesaid.

19. In a material handling system, a conduit for a gaseous conveyingmedium, means for feeding said conduit with material to be conveyedthrough said conduit by said gaseous medium, and electrical controlmeans for said material feeding means including photosensitive meansresponsive to the degree to which said gaseous medium is laden withmaterial, said photosensitive means including a member through whichlight may pass and which is disposed in sealing relation to a passagefor light formed in the wall of said conduit, a photoelectric cell,means for projecting a beam of light across the interior of said conduitand through said sealing member to said photoelectric cell, and meansfor directing a material-free gaseous medium across the inner face ofsaid sealing member to insure against the excessive accumulation ofmaterial thereon.

References Cited in the file of this patent UNITED STATES PATENTS1,191,072 Fessenden July 11, 1916 2,420,217 Allen May 6, 1947 2,514,333Mylting July 4, 1950 2,554,583 McFall May 29, 1951

